This invention relates to the electron gun assembly of a plural beam cathode ray tube and more particularly to ruggedizing improvements in a one-piece electrode member utilized in a multi-beam cathode ray tube electron gun assembly.
Cathode ray tubes, of the type commonly employed in color television applications, conventionally utilize electron gun assemblies from which a plurality of electron beams are projected to impinge the cathodoluminescent display screen of the tube. In certain gun assembly constructions, the first and second grid electrode members, such being normally the control and screen grid electrodes thereof, are often formed as substantially planar components oriented in substantially parallel planes and spaced apart superposed relationship. Conventionally, these electrode members are affixed to at least two longitudinal insulative support members of the gun assembly by supporting projections extending from the sides of the respective planar elements.
In multi-beam guns these planar electrodes commonly have several spatially related apertures formed therethrough to accommodate the respective electron beams generated within the structure. It is important that these several apertures be accurately and consistently spatially located relative to the related apertures of adjacent electrode members, and to the respective cathode surfaces from which the specific electron beams emanate.
Fabrication of the gun assembly involves embedment of the plurality of outwardly extending supporting projections of the respective electrode components into the temporarily heat-softened assembly support means; at which time, the support members on opposed sides of the assembly structure are pressured inward toward the electrode elements thereby forcing the supporting projections thereof into the softened support members. The compressive embedment pressure tends to exert a distorting force upon the several electrode members, this being especially critical to the planar members wherein a bowing or arcuate bending effect sometimes results. Such bowing, however slight, changes the aperture locations relative to those in the adjacent electrode members, thereby producing deleterious inter-electrode spacing relationships within a gun structure. These uncontrollable changes in the related aperture spacings are particularly troublesome in in-line gun constrictions wherein the first and second grid electode members often have related apertures of small diameters and close spacings. Since it is a common practice to utilize planar electrode elements for both the first and second grid electrodes, bowing conditions in one or both drastically aggravates the critical inter-electrode spacing characteristics resulting in pronounced inferior performance of the respective electron guns. Additionally, it has been found that a certain amount of distortion of a planar type electrode member is often aggravated by tube processing procedures and by welding pressures employed in effecting attachment of the electrode component to the associated connective lead in a gun assembly.